cytoskeleton

Definition: A network of molecular filaments (actin, microtubules, etc.) that provide a structure for the cytoplasm.

Ontology: Any of the various filamentous elements within the cytoplasm of eukaryotic cells that remain after treatment of the cells with mild detergent to remove membrane constituents and soluble components of the cytoplasm. GO:0005856

The term cytoskeleton embraces intermediate filaments, microfilaments, microtubules, and the microtrabecular lattice.

The various elements of the cytoskeleton not only serve in the maintenance of cellular shape but also have roles in other cellular functions, including cellular movement, cell division, endocytosis, and movement of organelles.

By continuous assembly-disassembly cycles, the cytoskeleton participates in several important functions in cellular processes such as locomotion, maintainance of cell shape, growth, cell division, secretion, adhesion, phagocytosis and cell-cell contact.

The cytoskeleton can also provide a structural link between the extracellular matrix and the nuclear envelope.

Cells can, by utilizing the cytoskeleton, influence neighbouring cells either by intracellular junctions or by effects on the extracellular matrix.

There are three main components of the cytoskeleton: microfilaments, intermediate filaments, and microtubules.

 The microfilaments are two twisted strands of proteins (actins) 7nm in diameter and can be up to several centimeters long. They are responsible for the movement of pseudopodia, the prey that is engulfed by Amoebae.

 The intermediate filaments is composed of eight microfilaments bound to form a rope like structure. It’s function is to maintain cells shape by holding all the different parts of the cell in an advanced web.

 The microtubules are tubes consisting of two proteins (tubulins). They control the movement of chromosomes during cell division, the movement of organelles within cytoplasm, and the movement of cilia and flagella.

Features

 microbial pathogenesis and cytoskeletal function
 cytoskeletal dynamics
 membrane-cytoskeleton adhesion
 cytoskeleton rearrangement - cytoskeleton reorganization
 cytoskeleton and cellular shape
 cytoskeleton and cellular movement
 cytoskeleton and cell division
 cytoskeleton and endocytosis
 cytoskeleton and movement of organelles

Pathology of the cytoskeleton (cytoskeletopathies)

 Pathology of the microfilaments (actins)

• Wiskott-Aldrich disease (WASP)

 Pathology of the microtubules (tubulins)

• Pathology of microtubule-associated proteins (MAPs)
  • taupathies (anomalies of the tau protein)

 Pathology of the intermediate filaments

• Pathology of the cytokeratins (cytokeratinopathies)
• Pathology of desmin (desminopathies)
• myofibrillar myopathies

Pathogenesis

 Abnormalities of the cytoskeleton underlie a variety of pathologic states. The cytoskeleton consists of microtubules (20 to 25 nm in diameter), thin actin filaments (6 to 8 nm), thick myosin filaments (15 nm), and various classes of intermediate filaments (10 nm). Several other nonpolymerized and nonfilamentous forms of contractile proteins also exist.

 Cytoskeletal abnormalities may be reflected by:

• (1) defects in cell function, such as cell locomotion and intracellular organelle movements
• (2) in some instances by intracellular accumulations of fibrillar material. Only a few examples are cited.

 cytoskeletal anomalies and cell injury

In cell injury, activation of proteases by increased cytosolic calcium may cause damage to elements of the cytoskeleton. In the presence of cell swelling, this damage results, particularly in myocardial cells, in detachment of the cell membrane from the cytoskeleton, rendering it susceptible to stretching and rupture.

See also

 cytoskeletal anomalies
 cytoskeletal lesions
 cytoskeletal dysfunction
 cytoskeletal polymers

• microtubules
• actins
• neurofilaments

References

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